Paper filter element center tube

ABSTRACT

Annular filter elements for outside-in operation ordinarily include a center tube for support against inward collapse, and this disclosure concerns a center tube formed from a flat sheet metal stamping including a longitudinally extended backbone and interspaced ribs extending laterally from this backbone and having free ends, the stamping being formed into a cylinder with the backbone extending axially and the ribs extending circumferentially and their free ends fastened.

O United States Patent 1 1 11 1 3,7 86,926

Wilhelm Jan. 22, 1974 [54] PAPER FILTER ELEMENT CENTER TUBE 3,054,5079/1962 Humbert, Jr. et a1. 210/493 [75] Inventor: John R. Wilhelm, PerthAmboy, e

Primary Exammer-Sam1h N. Zaharna Assistant Examiner-Robert H. Spitzer[73] Ass1gnee: Purolator, Inc., Rahway, NJ. Attorney, Agent or Firmcharles Spencer [22] Filed: Nov. 17, 1971 21 Appl. No.: 199,565 ABSTRACTAnnular filter elements for outside-in operation ordi- [52] US. Cl.210/497 narlly include a Center tube for pp against inward [51] Int. ClBOld 29/04 Collapse and this disclosure concerns a Center tube 58 Fieldof Search..... 210/43, 436, 437,439,446, formed from a fiat Sheet metalStamping including 2 0 457 4 3 4 4 4 5 4 7 493 4 longitudinally extendedbackbone and interspaced ribs 497, 498, 5 extending laterally from thisbackbone and having free ends, the stamping being formed into a cylinderwith I 5 References Cited the backbone extending axially and the ribsextending UNITED STATES PATENTS circumferentially and their free endsfastened.

2,843,269 7/1958 Dudinec 210/483 X 1 Claim, 5 Drawing Figures PAPERFILTER ELEMENT CENTER TUBE This invention relates to annular fluidfilter elements of the type commonly used either replaceably orpermanently fixed in casings of automotive oil filters and possiblyfilters of other types.

Customarily such elements are adapted for outside-in operation, meaningthat the flow of oil, or possibly other fluid, is from the outerperiphery of the element through the element and from the inside of theelement and away from the inside of the element. Therefore, the annularelement usually incorporates a metal perforated tube, called a centertube, on its inside and supporting the element against inward collapse,keeping in mind that the filter media is ordinarily pleated paper,fibrous material or the like, unable to withstand safely the pressuredifferential existing between the outside and the inside of the element.

Prior art filter tubes have included perforated sheet metal bent into acylinder held in shape by a longitudinally extending mechanicallock-seam, the formation of the perforations representing a scrap losswhich is undesirable and ordinarily not providing as free a flow of oilas might be desired. Other disadvantages are outlined in the US. DudinecPat. No. 2,843,269, dated July I958, disclosing and claiming animprovement. However, this improvement has the disadvantage of requiringthe use of relatively expensive special forming dies and the ends of thecenter tube are formed by axially offset members as contrasted to thecompletely flush ends of the previously described prior art center tubewhich is more generally used.

The object of the present invention is to provide a center tube havingat least the same strength as the more conventional center tube made ofperforated sheet metal while providing a larger open area for drainageor oil flow and which may be stamped from flat sheet metal without scraploss while, if desired, providing the tube with completely flush ends.

As a brief summary of the present invention, a center tube for thedescribed oil or other fluid filter element is formed from a flat sheetmetal stamping having a pattern including a longitudinally extendedbackbone and interspaced ribs extending laterally from this backbone andhaving free ends, the transverse width and the interspacing of the ribsof this stamping being of substantial equal dimensions so that thematerial stamped from the spaces between the ribs form the ribs of anadjacent stamping. The term stamping, as used herein, is intended tomean the use of cooperating dies which are brought together to shear thesheet metal and form the described pattern of product. These dies arepreferably provided with corrugations which corrugate the resultingstamping throughout its backbone and ribs with the corrugationsextending longitudinally with respect to the ribs and, therefore,circumferentially with respect to the finished tube. Also preferably thedies are shaped to form a longitudinally extending stiffening depressionin the backbone. This stamping is then bent into a cylindrical tube andthe free ends of the ribs are overlapped and interfastened by means ofeither spot welding or possibly some other method suitable forinterfastening sheet metal parts.

Specific examples of the present invention are illustrated by theaccompanying drawings in which:

FIG. 1 is a longitudinal section showing an element incorporating thecenter tube of the present invention;

FIG. 2 is a plan of the stamping formed from the flat sheet metal;

FIG. 3 is an elevation showing the finished center tube;

FIG. 4 is a cross section taken on the line 4-4 in FIG. 3; and

FIG. 5 shows a plan of a possible modification.

More specifically referring to these drawings, FIG. I shows a typicalannular pleated paper filter media 1 supported against internal collapseby the center tube CT of the present invention and typical end caps 2such as are used to confine the flow of oil or other fluid and force itto travel from the outer periphery of the media 1 and through the latterand through the center tube CT and from the inside of the center tube.

FIG. 2 shows the metal stamping, keeping in mind that a multiplicity ofthese may be stamped from a larger piece of sheet metal with all of thestampings identical. This stamping includes the backbone 3 which extendslongitudinally and the interspaced ribs 4 which extend laterally inopposite directions from this backbone 3 and the free ends 5 of theseribs. The transverse width A of the ribs and the interspacing B of theseribs are of equal dimensions for the reason previously described. Theribs are all of the same length. The ribs of the backbone are stampedwith the corrugations 6 which extend longitudinally with respect to theribs 4 and transversely with respect to the backbone 3, and the backboneis stamped with the rib 7 which extends longitudinally with respect tothe backbone. This rib is in the form of a depression which terminatesnear the ends of the backbone, for example, at points approximately atthe center lines of the end-most ribs.

FIGS. 3 and 4 show how this stamping is bent into a cylindrical tubewith its end portions overlapped with their corrugations interfitting,with spotwells 8 interfastening each of the overlapped end portions 5aof all of the ribs.

The corrugations 6 permit the use of relatively light gage sheet metalwhile providing adequate collapse strength, while the rib 7 providesadequate column strength and resistance to bending in general.

Going back to FIG. 2, it can be seen that the ends 5 of the ribs and thebases of these ribswhich define the spaces between them are stamped sotheir corners are all rounded, each with the same radius to permit themultiple stamping from flat sheet metal without scrap loss previouslyreferred to. As shown by FIG. 4, the stamping is bent so that the rib 7of the backbone 3 projects inwardly.

In the case of the completed tube, the corrugations 6 extendcircumferentially while the rib 7 extends axially.

The stamping shown by FIG. 5 represents a modification which may or maynot include the corrugations previously described. In this case the ribs4a extend laterally or from one side only of the backbone 3a instead ofin opposite directions as previously described. To interfasten the freeends 5a of this modification, these ends are overlapped on the backbone3a and in this manner interfastened. The first example is the presentlypreferred form of the present invention.

What is claimed is:

1. An annular fluid filter element for outside-in operation andincluding a center tube for support against inward collapse; wherein theimprovement comprises said center tube being formed from a flat sheetmetal are of substantially equal dimensions, said backbone and said ribsare circumferentially corrugated, said backbone has a longitudinallyextending stiffening depression, and said free ends are overlapped andconnected together.

1. An annular fluid filter element for outside-in operation andincluding a center tube for support against inward collapse; wherein theimprovement comprises said center tube being formed from a flat sheetmetal stamping including a longitudinally extending backbone andinterspaced ribs extending laterally from this backbone and having freeends, said stamping being formed into a cylinder with the backboneextending axially and the riBs extending circumferentially and theirfree ends interfastened, and in which the transverse width and theinterspacing of said ribs of said stamping are of substantially equaldimensions, said backbone and said ribs are circumferentiallycorrugated, said backbone has a longitudinally extending stiffeningdepression, and said free ends are overlapped and connected together.